Separation of cineoles from hydrocarbons of similar boiling range by azeotropic distillation with phenols



Patented Jan. 18, 1949 .UNITED STATES PATENT OFFICE 2,459,432 SEPARATIONOF CINEOLES FROM HYDRO- CARBONS OF SIMILAR BY AZEOTROPIC DISTILLATIONPHENOLS Harold E. Johnson, Hercules Powder BOILING RANGE WITHWilmington, Del., assignmto Company, Wilmington, Del., a corporation ofDelaware Nobrawingl Continuation of application Serial No. 726,958,February 6, 1947. This August 20, 1948, Serial No.

application 45,443

9 Claims. c aos-42) This invention relates to a process for separatingthe cineole and hydrocarbon constituents of a mixture containingcineoles and hydrocarbons of similar boiling range and, moreparticularly, to a process of separating such constituents by;

fractional azeotropic distillation.

sequently conventional fractional distillation procedures have not beensuccessful in emciently separating the cineoles from the components ofthe mixture of hydrocarbons. Various methods have been proposed,however, for effecting the separation of cineoles and hydrocarbons ofsimilar boiling range, and the more successful methods haveinvolveddistillation of a cineole-hydrocarbon mixture in the presence of certaincresols. The cineoles form stable complexes with the mand p-cresols atlow temperatures and pressures, and it therefore has been possible bymaintaining suiiiciently low temperatures and pressures to distill ofithe more volatile hydrocarbons. These methods have been somewhatdisadvantageous, however, due to the fact that atmospheric pressurescould not be utilized. At atmospheric pressures and the concurrentlyhigher temperatures necessary to distill the hydrocarbons thecineole-cresol complexes are not stable, consequently the cineoles arenot prevented from distilling with the hydrocarbons. These methods alsohave been disadvantageous in not being able to use phenol as thecomplex-forming agent, the boiling point of phenol being too close tothat of any of the cineoles and permit formation of stable complexeswith the cineoles. I

Now in accordance with this invention, it has been found that phenol maybe utilized to separate the cineole and hydrocarbon constituents of amixture containing cineoles and hydrocarbons similar boiling range bysubjecting the mixture of cineoles and hydrocarbons to fractionalazeotropic distillation in the presence of phenol as the azeotropicagent. In contrast with previous processes, which have not used aphenolic compound such as phenol to form constant boiling azeotropicmixtures, phenol is used in the process in accordance with thisinvention for the purpose of forming constant boiling mixtures with thecineoles and the hydrocarbons contained in a mixture composed of thecineoles and hydrocarbons of similar boiling range. It also has beenfound in accordance with this invention that the azeotroplc mixtureswhich phenol forms with 1,4-cineole, 1,8-cineole, and the hydrocarbonsof similar boiling range may be separated into their individualcomponents by subjecting .each azeotropic mixture to fractional steamdistillation.

In carrying out the process in accordance with this invention, phenoland a cineole-hydrocarbon mixture in which the cineole content maybe,for

example, about 55%, are chargedinto a heating hydrocarbons to pctfitted. with a packed column having about theoretical plates. Thereaction mixture then is heated to distillation temperatures andfractional distillation carried out. This results in the separation ofthree main azeotropic mixtures; namely, hydrocarbon-phenol,1,4-cineole-phenol, and 1,8-cineole-phenol, the hydrocarbons -formingminimum boiling azeotropes and the cineoles forming maximum boilingazeotropes with the phenol. In the case of the maximum boilingcineole-phenol azeotropes, the 1,8- cineole-Dhenol azeotrope bollshigher than does the 1,4-cineole-phenol azeotrope. Following separationof the individual hydrocarbon-phenol tillation for the purpose ofrecovering the hydrocarbons, the 1,4-cineole, and the 1,8-cineole,respectively.

The following examples constitute specific embodiments of the process inaccordance with this invention. All parts are parts by weight.

Example 1 To a heating pot fitted with a '75-plate packed column wascharged 1516 parts of phenol was distilled to a constant azeotropes.phenol-cineole-hydrocarbon mixdistilled. A reflux ratio v 3 ture thenwas distilled batchwise at a reflux ratio of approximately 75 to 1, and0.5% fractions were removed as overhead product throughout the.

course of the distillation. The pressure was main- \tained at 100 mm..and the throughput was maintained at a constant pressure drop of 15 mm.of ,mercury.-

The various 0.5% hydrocarbon-phenol fractions'boiled over a range of83.6 to 110 C. at a,

pressure of 100 mm., and when combined on the basis of boiling point andrefractive index represented a total fraction of 1460.3 parts. Likewise,the .1,4-cineole-phenol azeotrope fractions boiled over a range of1-19.3 to 120 C. at a pressure'of 100mm. and on combination representeda total fraction of 2039.2 parts. The 1,8-cineole-phenolazeotropefractions boiled over a range of 121 to 121.2 C. at a pressure of 100mm. and on com-. bination represented a total fraction of 135912 parts.The residue remaining in the heating pct amounted to 148 parts and thatremaining in the Following the general procedure utilized in Example 1,1001 parts of the cineole-hydrocarbon mixture of Example 1 and 600 partsof phenol were charged to the heating pot and fractionally "columnpressure was maintained at 100 mm. and

' removed as overhead product. The fractions were the throughput wasmaintained at a constant pressure drop of 10 mm. of mercury. Through thecourse of the distillation 1.5% fractions were recombined on the basisof boiling point and refractive index. Sincethe amount of phenolutilized was sufllcient, to remove completely as their azeotropes thehydrocarbons and the 1,8-cineole, but insuificient to remove completelyas its azeotrope the 1,4-cineole, the four fractions collectedconstituted the hydrocarbon-phenol azeotrope, 1,4 -cineo1e, the1,4-cineole-phenol azeotrope, and the-1,8-cineole-phenol azeotrope. Thehydrocarbon-phenol azeotrope distilled over a range of 88 to 105 C. at100 mm. and represented 268.0 The 1,4-cineole fraction distilled between105 and 106 C. at 100 mm. and represented 467.8 parts. The1,4-cineole-phenol azeotrope distilled between 118 and 119 C. at 100 mm.and represented 338.4 parts. The 1,8-cineole-phenol azeotrope fractionsdistilled over a temperature range of 119 to 121 C. at 100 mm. andconstituted 468.4 parts. A total of 43 parts residue was collected fromthe heating pot and column and represented 3.2% of the total charge. Adistillation loss of 0.9% was incurred.

Example 3 To a heating pot fitted with a 20-plate column containing anautomatic separatory head was charged 424 parts of .the1,8-cineole-phenol azeo trope obtained in Example 2. The cineole-phenolazeotrope contained in the heating pot was subjected to steamdistillation at atmospheric pressure, the temperature being 97 C. Duringthe distillation the water condensate in the separatory head was kept attotal reflux and the 1,8-cineole layer was distilled at a reflux ratioof approximately 13 to 1. There was recovered 136.7 parts of 1,8-cineolewhich had a refractive index of 1.4573 at 20 C. and was essentially 100%pure. The 1,8-cineole had a boiling point of 107.9 C. at

of 75 to 1 was used, the

4 100 mm., a density of 0.92584 at'20 C., and a congealing point of 1.5C. By calculation from ultraviolet absorption analysis 33% of the l,8-cineolephenol azeotrope was 1,8-cineole. On this basis 97.7% of the1,8-cineole estimated to be in the phenol azeotrope was recovered.

Example 4 Following the procedure of Example 3, 744 parts of the1,4-cineole-phenol azeotrope obtained in Example 1 was fractionallysteam distilled at atmospheric pressure, the temperature being 98 C.

Throughout the distillation approximate 1.5%

fractions of 1,4-cineole were removed overhead. These fractions had aconstant refractive index of 1.4446 at 20 C. and on being combinedamounted to 415.3 parts. As indicated by ultraviolet absorption analysisforthe amount of 1,4- cineole in the 1,4-cineole-phenol azeotrope, thisrepresented a 97.7% recovery of 1,4-cineole. The 1,4-clneole had aboiling point of 1051 to 105.3 C. at 100 mm., a density of 0.90075 at 20C. and an approximate congealing point of -46.2 0.

Although the process in accordance with this invention has" beenillustrated by the examples in connection with a cineole-hydrocarbonmixture containing cineoles, the amount of cineoles in relation to thehydrocarbons may be varied considerably. The process may be utilizedwith any cineole-hydrocarbon mixture, but it generally is moreapplicable to cineole-hydrocarbon mixtures containing from about 15 toabout 90% total cineoles. From practical considerations the range ofcineole content should. befrom about 50 to about 75%. Also, although thecineolehydrocarbon mixture used in the examples contained both1,4-cineole and Lil-cineole, the process is operable withcineole-hydrocarbon mixtures containing only one of the cineoles. Suchmixtures are obtained, for example,'by the partial dehydration of either1,4-terpin or 1,8-terpin for the purpose of obtaining 1,4-cineole'or1,8-

. cineole, respectively.

parts.

In carrying out the fractionalazeotropic distillation of this invention,Examples 1 and 2 have shown the use ofabout 1.2 parts and about 0.6

part, respectively, of the azeotropic agent, phenol,

per part of the cineole-hydrocarbon mixture. In general, 'however, theparts by weight ratio of phenol to the mixture containing cineoles andhydrocarbons of similar boiling range may be from about 0.3:1 to about4:1. A desirable range upon this basis is from about 0.3:1 to about0.6:1, preferably from about 0.3:1 to about 05:1, in case it is desiredto eiiect the type of separation shown in Example 2. In this examplethere was sufiicient phenol to remove completely as constant boilingazeotropes the hydrocarbons and the 1,8- cineole, but insufficientphenolto remove completely as its azeotrope the 1,4-cineole. The latter wastherefore permitted to distill partially as its azetrope and partiallyas free 1,4-cineole. It is possible by decreasing further the amount ofphenol used in Example 2'to separate the 1,4- cineole only as free1,4-cineole. This generally may be accomplished by using a weight ratioof phenol to the cineole-hydrocarbon mixture in the range of about 0.3:1to about-05:1. Operation of such a process depends upon the fact that1,4-cineole forms a more unstable azeotrope with phenol than does1,8-cineole, and that in the presence of a relatively insuiiicientamount of phenol will not form a phenol azetrope. This modification ofthe process effects a saving in the amount of phenol necessary and isadvantag'eous for obtainingpure 1,8-cineole since a a wide temperaturedifierential is established behydrocarbons in the form oftheirrespective azeotropes with phenol, the parts by weight ratio of phenolto the mixture containing cineoles and hydrocarbons of similar boilingrange should be from about 1.2:1 to about 4:1, a preferable range inthis instance being from about 3:1 to about 4:1. With this amount ofphenol there is an effective working temperature differential of about10 to C. between the minimum boiling hydrocarbon-phenol azeotrope andthe maximum boiling cineole-phenol azeotropes, and there also is anoperatin temperature diflerential of about 12 C. between the twocineole-phenol azeotropes. Although the temperature differential betweenthe two cineole-phenol azeotropes is .rather small, this is compensatedby the difference in percent composition of the .two azeotropes. Sincethe 1,4-cineole-phenol azeotrope contains approximately 50% 1,4-cineoleand the 1,8-cineole-phenol azeotrope contains about 33% 1,8-clneole,complete separation of the two azeotropes is possible in an eiilcientcolumn operating at a temperature difierential of l .2 C. Columns havingabout 75 to about 200 theoretical plates are satisfactory, particularlywhen operated'at a refiex ratio between about 75:1 to about 150:1,preferably between about 75:1 toabout 90:1.

-In the examples the azeotropic dlstillations with phenol were carriedout at an absolute pressure of 100mm. of mercury. The process inaccordance with this invention, however, is operable at atmosphericpressures and, in general, the azeotropic distillation may be carriedout between about 30 and about 760 mm. of mercury. A preferable range isbetween about '15 and about 250 mm. of mercury, and a particularlyapplicable range is between about 100 and about 200 mm. of mercury.

As shown in Examples 3 and 4 the cineolephenol azeotropes may be brokenby subjecting them to fractional steam distillation. Such a process alsomay be utilized to separate the components of the hydrocarbon-phenolazeotrope.

In the fractional steam distillation of the a Y cineole-phenolazeotrope, for example, there is formed an azeotropic distillatecomposed of water, phenol, and Lil-cineole. In the fractionating colnmn,which is equipped with an automatic separatory head adapted to separatethe 1,8-cineole and water phases and return the latter downward throughthe column to the distillation pot, as the cineole-water-phenolazeotrope ascends, the phenol is. extracted from the azeotrope andwashed down the column by the hot water returning from the separatoryhead. Following extraction of the phenol, the residual mixture of waterand 1,8- cineole ascends the column and is separated into its componentsin the separatory head, the 1,8- cineole being withdrawn under partialor total takeoil, substantially free of phenol. The fractional steamdistillation is likewise applicable to breaking the 1,4-cineole-phenoland hydrocarbon-phenol azeotropes. Examples 3 and 4 have shown the usein the steam distillation step of a fractionating column having 20theoretical plates, but columns having up to 50 theoretical plates mayadvantageously be used. These columns should be operated at a refluxratio of about 13:1 relative to the oil layer. since lower tion of1,4-cineole and 1,8-clneole from hydrocarbons-of similar'boiling rangeand also permits effective separation of the two cineoles from eachother. The cineolesrecovered according'to the process of this inventionare'of a higher state of purity than it-has been possible to obtain, byprevious processes. In contrast to prior methods for efiectingseparation of cineoles from hydrocarbons of similar boiling range, thepresent process may be operated at atmospheric pressures and theconcurrently higher temperatures. The process is unique in that only twostages of fractionation are required to obtain pure clne'oles. First,the hydrocarbon and cineole azeotropes are fractioned in an eillcientcolumn and, second, the resulting phenol azeotropes are broken byfractional steam distillation. resulting in the recovery of individualfractions of pure 1,4-cineole, 1,8-cineole and hydrocarbons. Thecineoles obtained by the present process conform to U. S. P.speciflcations and are therefore indicative of the commercial merit ofthe process.

This application is a continuation of the application Serial No. 726,958filed February 6, 1947'by Harold E. Johnson and Harold M. Spurlinhearing the title "Separation of cineoles from hydrocarbons of similarboiling range by azeotroplc distillation with phenols.

What I claim and desire to protect by Letters Patent is:

1. The process of' separating the cineole and hydrocarbon constituentsof a mixture containing cineoles and hydrocarbons of similar boilingrange which comprises subjecting said mixture to fractional azeotropicdistillation in the presence of phenol as the azeotropic agent.

2. The process of separating the cineole and hydrocarbon constituents ofa mixture containing cineoles and hydrocarbons of similar boiling rangewhich comprises. subjecting said mixhire to fractional .azeotropicdistillation in the presence of phenolas the azeotropic agent, theweight ratio of phenol to said mixture being from about 0.321 toabout4:1.

3. Theprocess of separating the cineole. and hydrocarbon constituents ofa mixture containing cineoles and hydrocarbons of similar boiling rangewhich comprises subjecting said mixture to fractional azeotropicdistillation in the presence of phenol as the azeotropic agent, theweight ratio of phenol to said mixture being from about 0.3:1 to about0.5:1.

4. Theprocess of separating the cineole and hydrocarbon constituents ofa mixture containing cineoles and hydrocarbons of similar boiling rangewhich comprises subjecting said mixture to fractional azeotropicdistillation in the presence of phenol as the azeotropic agent, theweight ratio of phenol to said mixture being from about 3:1 to about4:1.5

5. The process of separating the cineole and hydrocarbon constituentsofa mixture containing cineoles and hydrocarbons of similar boiling rangewhich comprises subjecting saidmixture to -fractional azeotropicdistillation at a pressure between about 30 and about 760 mm. of mercuryv 7 6. The process of separating the cineole and hydrocarbonconstituents of a mixture containing cineoles and hydrocarbons ofsimilar boiling fractional azeotro'pic distillation in the presence ofphenol as the azeotropic agent, and recovering hydrocarbon-phenol andcineole-phenol azeotropes as separate fractions.

8. The process of separating the cineole and hydrocarbon constituents ofa mixture containing 1,4-cineole, 1,8-cineole and hydrocarbons ofsimilarboiling range which comprises subjecting said mixture to fractionalazeotropic distillation in the presence of phenol as theazeotropicagent, the weight ratio of phenol to said mixture being fromabout'0.3:1 to about 0.5:1, and recovering as separate fractions thehydrocarbon-phenol azeotrope, 1,4-cineole, and the 1,8-cineole-phenolazeotrope.

9; The process of separating the cineole and hydrocarbon constituents ofa mixture containing 1,4-cineole, 1,8-cineo1e and hydrocarbons ofsimilar boiling range which comprises subjecting said mixture tofractional azeotropic distillation in the presence of phenol as theazeotropic agent, the weight ratio of phenol to said mixture being fromabout 3:1 to about 4:1, and recovering as separate fractions thehydrocarbon-phenol, 1,4- cineole-phenol and 1,8-cineole-phenolazeotropes.

- HAROLD E. JOHNSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,090,620 Bibb Aug. 24, 19372,315,986 Scrutchfield Apr. 6, 1943 2,353,319 Sheflield July 11, 1944

